Use of bentonite for improving plant growth-related traits

ABSTRACT

The present invention relates to a slurry comprising water, bentonite, and a compound selected from fertilizer, a plant growth regulator, a fungicide and an insecticide. The present invention also relates to an agricultural product comprising a slurry comprising water and bentonite, and a plant propagative material. Methods of using the bentonite to enhance a growth-related trait, such as drought tolerance, in a plant are also described.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/441,523,filed Feb. 24, 2017, now U.S. Pat. No. 10,251,397, issued Apr. 9, 2019,which, in turn is a continuation under 35 U.S.C. § 111(a) ofInternational Application No. PCT/US2016/018370, filed Feb. 18, 2016which, in turn, claims priority to U.S. Provisional Patent ApplicationNo. 62/118,198 filed on Feb. 19, 2015, the contents of each of which areexpressly incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to the use of bentonite for enhancing agrowth-related trait in a plant.

BACKGROUND OF THE INVENTION

Stand establishment refers to the production of a uniform population ofhealthy seedlings of agricultural crops. The stand of an agriculturalcrop may be established through direct seeding into the field, or by theplanting of transplants. Successful crop production and optimum yieldscan be accomplished only when maximum stand establishment is achieved.(Grassbaugh et al., 1998, Sci. agric., Piracicaba, 55 (Edicao Especial):116-120). Stand reduction generally results in reduced yields andvariable crop quality. Several factors contribute to stand establishmentin the production of agricultural crops. Environmental factors such asdrought, temperature stress and unfavorably soil conditions, as well aspathogens and insects that attack seeds and seedlings can all contributeto reduced stands (Orzolek, 1991, HortTechnology 1: 78-81). Fordirect-seeded crops, uneven germination results in seedlings of varioussizes and gaps in the planting row, which can ultimately result inreduced yields. For transplanted crops, poor transplant survival ratesor slow initiation of plant growth after transplanting can result inreduced plant populations and uneven stands. In addition, culturalpractices such as herbicide and insecticide applications aftertransplanting or seed emergence may be less effective in fields havingnonuniform growth (Bennett et al., 1992, HortTechnology 2(3): 345-349).Plants of different sizes within a field population may also causeproblems in timing sidedress applications of fertilizers (Ford, 1987,Crops and Soils Magazine, p. 12-13, April/May, 1987). Thus, measures tolessen the impact of environmental stresses and various pests are vitalin the successful establishment of agricultural crop stands. The abilityof plants to survive stresses imposed by environmental conditions andpest infestations greatly depends on the initial vigor of the stand atestablishment.

Dry seed coating is one method that has been developed to improveestablishment of direct-seeded crops. For example, US 2012/0220454describes seed coating compositions that may comprise more than onelayer, for example, a first layer comprising a film forming layer, asecond layer comprising a binding agent, and a third layer comprising awetting agent. See US 2012/0220454, paragraph [0019]. In addition US2012/0220454 teaches that the seed coating compositions can flow betterthrough a seeding mechanism, because their surface is smoother than thatof non-coated seed. See US 2012/0220454, paragraph [0021].

US 2010/0267554 describes coating seeds with a wetting agent such ascopolymers, block copolymers, alcohol ethoxylates, nonylphenolethoxylates, ethylene oxide/propylene oxide block copolymers, andalkylpolyglycosides for planting in hydrophobic soils. See US2010/0267554, paragraphs [0022] and [0023].

Despite the potential advantages of seed coating technologies, a needstill exists for improving stand establishment for direct-seeded andtransplanted food crops and ornamental plants.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a composition comprising a slurrycomprising at least about 50% w/w of water and from about 1% to about50% w/w of bentonite; and a plant propagative material. In oneembodiment, the slurry further comprises a compound selected from thegroup consisting of a fertilizer, a plant growth regulator, a fungicide,an insecticide, an amino acid, a peptide, a protein, and a nucleic acid.In one embodiment, the plant growth regulator is selected from the groupconsisting of auxins, giberellins, cytokinins, ethylene-relatedcompounds, abscisic acid, brassinosteroids, jasmonates, polyamines,karrikins, and any combination thereof. In another embodiment, theslurry further comprises a fertilizer comprising nitrogen, and thenitrogen is at a concentration from about 10 ppm (w/w) of the slurry toabout 2000 ppm (w/w) of the slurry. In another embodiment, the slurryfurther comprises a plant growth regulator at a concentration from about10 ppm to about 1000 ppm. In one embodiment, the plant propagativematerial is a seed.

In another aspect, the invention provides a composition comprising asupersaturated bentonite slurry comprising bentonite and water; and aplant propagative material.

In another aspect, the invention provides a supersaturated bentoniteslurry comprising bentonite, water, and a compound selected from thegroup consisting of a fertilizer, a plant growth regulator, a fungicideand an insecticide.

In another aspect, the invention provides a slurry comprising water,from about 10% (w/w) to about 50% (w/w) of bentonite, and a compoundselected from the group consisting of a fertilizer, a plant growthregulator, a fungicide and an insecticide.

In one embodiment, the plant growth regulator is selected from the groupconsisting of auxins, giberellins, cytokinins, ethylene-relatedcompounds, abscisic acid, brassinosteroids, jasmonates, polyamines,karrikins, and any combination thereof. In another embodiment, theslurry comprises a fertilizer comprising nitrogen, and the nitrogen isat a concentration from about 10 ppm (w/w) of the slurry to about 2000ppm (w/w) of the slurry. In another embodiment, the slurry comprisesfrom about 10 ppm to about 1000 ppm of the plant growth regulator.

In another aspect, the invention provides a method of enhancing agrowth-related trait in a plant propagative material relative to acontrol plant propagative material, comprising a) applying a slurrycomprising bentonite and water to a plant growth medium; and b)introducing the plant propagative material into the plant growth mediumcontaining the slurry, wherein the growth-related trait of the plantpropagative material is enhanced relative to a control plant propagativematerial that is not treated with the slurry.

In one embodiment, the growth-related trait is selected from the groupconsisting of total seed germination, rate of seed germination, plantbiomass, insect tolerance, herbivore tolerance, and drought tolerance.In another embodiment, the growth-related trait is enhanced underdrought conditions. In another embodiment, the slurry further comprisesat least one compound selected from the group consisting of afertilizer, a plant growth regulator, a fungicide, an insecticide, anamino acid, a peptide, a protein, and a nucleic acid. In anotherembodiment, the plant growth regulator is selected from the groupconsisting of auxins, giberellins, cytokinins, ethylene-relatedcompounds, abscisic acid, brassinosteroids, jasmonates, polyamines,karrikins, and any combination thereof.

In one embodiment, the bentonite is selected from the group consistingof sodium bentonite and calcium bentonite. In one embodiment, the plantpropagative material is a seed.

In another embodiment, the slurry is a supersaturated bentonite slurry.In another embodiment, the slurry is applied to a discrete area of theplant growth medium.

In another aspect, the invention provides a method of enhancing agrowth-related trait in a plant propagative material relative to acontrol plant propagative material, comprising a) contacting a slurrycomprising bentonite and water with a plant propagative material; and b)introducing the plant propagative material contacted with the slurryinto a plant growth medium; wherein the growth-related trait of theplant propagative material is enhanced relative to a control plantpropagative material that is not treated with the slurry.

In one embodiment, the growth-related trait is selected from the groupconsisting of total seed germination, rate of seed germination, plantbiomass, insect tolerance, herbivore tolerance, and drought tolerance.In another embodiment, the growth-related trait is enhanced underdrought conditions.

In one embodiment, the slurry further comprises at least one compoundselected from the group consisting of a fertilizer, a plant growthregulator, an insecticide, a fungicide, an amino acid, a peptide, aprotein, and a nucleic acid. In one embodiment, the plant growthregulator is selected from the group consisting of auxins, giberellins,cytokinins, ethylene-related compounds, abscisic acid, brassinosteroids,jasmonates, polyamines, karrikins, and any combination thereof.

In one embodiment, the bentonite is selected from the group consistingof calcium bentonite and sodium bentonite. In another embodiment, theplant propagative material is a seed. In one embodiment, the slurry is asupersaturated bentonite slurry. In one embodiment, the plant growthregulator is selected from the group consisting of auxins, giberellins,cytokinins, ethylene-related compounds, abscisic acid, brassinosteroids,jasmonates, polyamines, karrikins, and any combination thereof.

In one embodiment, the slurry further comprises a compound selected fromthe group consisting of an amino acid, a peptide, a protein, and anucleic acid.

In another aspect, the invention provides a method of enhancing agrowth-related trait in a plant propagative material relative to acontrol plant propagative material, comprising a) applying bentonite toa discrete area of a plant growth medium; and b) introducing the plantpropagative material into the discrete area of the plant growth mediumcontaining the bentonite, wherein the growth-related trait of the plantpropagative material is enhanced relative to a control plant propagativematerial that is not treated with the bentonite.

In one embodiment, the bentonite is applied at a rate of less than about1000 kg/acre. In another embodiment, the bentonite is applied to lessthan 50% of the surface of the plant growth medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows slurry comprising bentonite and water placed in theplanting holes in potting soil before planting of sunflower seeds.

FIG. 2 shows sunflower seedlings 12 days after planting. Sunflower seedswere untreated (control) or treated with a green bentonite and 200 ppmIAA slurry (green bentonite+IAA), or a bentonite and MIRACLE-GROfertilizer slurry (bentonite+fertilizer) at the time of planting. In thebentonite+fertilizer treatment group, the seeds in the top three potswere treated with white bentonite and fertilizer and the plants in thebottom three pots were treated with green bentonite and fertilizer.

FIG. 3 shows sunflower seedlings 12 days after planting. Sunflower seedswere treated with a white bentonite slurry, a green bentonite slurry, ora white bentonite and 200 ppm IAA slurry (white bentonite+IAA) at thetime of planting.

FIG. 4 shows sunflower seedlings 18 days after planting. Sunflower seedswere untreated (control) or treated with a green bentonite and 200 ppmIAA slurry (green bentonite+IAA) or a bentonite and MIRACLE-GROfertilizer slurry (bentonite+fertilizer). In the bentonite+fertilizertreatment group, the seeds in the top three pots were treated with whitebentonite and fertilizer and the plants in the bottom three pots weretreated with green bentonite and fertilizer.

FIG. 5 shows sunflower seedlings 18 days after planting. Sunflower seedswere treated with a white bentonite slurry, a green bentonite slurry, ora white bentonite and 200 ppm IAA slurry (white bentonite+IAA) at thetime of planting.

FIG. 6A shows slurry comprising bentonite and water placed in theplanting holes in potting soil before planting of sunflower seeds. FIG.6B shows sunflower seedlings approximately 10 days after planting.

FIG. 7 shows a diagram of the cups filled with potting soil formeasurement of water retention ability of the bentonite slurry.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the use of a bentonite slurry forenhancing a growth-related trait in a plant. Unlike previously used seedcoatings, the water-based slurry comprising bentonite of the inventionimmediately introduces a hydrated microcosm that induces seedgermination. For example, the slurry provides a hydratedmicroenvironment to the seed that keeps the seed shell moist andpromotes water absorption into the shell. This in turn allows the shellto swell and eventually crack and initiate germination. Intermittentdrought stress is mitigated, as the slurry volume maintains a hydratedenvironment to promote seed shell swelling and germination. Once theseed shell has swollen and cracked, plant growth regulators andfertilizer in the slurry can enhance germination and rooting activityand expedite emergence of the seedling from the soil and early growth ofthe developing seedling.

Bentonite is a naturally absorbent clay consisting mostly ofmontmorillonite, which is part of the smectite group of clays. It is asilicate bilayer that sandwiches a cation (e.g., Na, Ca, or Mg), and ishygroscopic to varying extents. The different types of bentonite arenamed after the dominant element which they comprise, for examplepotassium (K), sodium (Na), calcium (Ca), aluminum (Al), or magnesium(Mg). There are two main classes of bentonite used for industrialpurposes: sodium bentonite and calcium bentonite. When mixed with water,sodium bentonites exhibit a greater degree of swelling, a greater degreeof dispersion, and better plastic and rheological properties thancalcium bentonites. See Inglethorpe et al., 1993, Bentonite, IndustrialMineral Laboratory Manual, Technical Report WG/93/20, Mineralogy andPetrology Series, British Geological Survey, pages 1-116. For example,sodium bentonite has the ability to absorb four to five times its ownweight in water and can swell five to fifteen times its dry volume atfull-unconfined saturation.

The Swell Index or Free Swell test procedure is typically used todetermine the swelling characteristics of bentonite. Several methods arewell known in the art to determine the swelling characteristics ofbentonite, including the Swell Index or Free Swell test. For example,one test method involves placing a 100 gram sample of bentonite in asix-inch diameter cylinder equipped with a porous plate/dial gaugeindicator. The apparatus is placed in a pan of water for twenty-fourhours, at which time the dial gauge is read for the swell increase.Results of this index test are used to determine the swellingcharacteristics of the bentonite sample. Because of its colloidalproperties, bentonite is often used in drilling mud for oil and gaswells and boreholes for geotechnical and environmental investigations.Calcium bentonite is an adsorbent of ions in solution. Potassiumbentonite is a potassium-rich illitic clay formed from alteration ofvolcanic ash. White bentonite is derived from weathered volcanic ash andis predominately calcium bentonite which has a high cation exchangecapacity and low crystalline silica (cristobalite). Green bentonite maybe a sodium bentonite or may contain other cations. The green color ofgreen bentonite results from Fe⁺⁺ ions contained in the bentonite. Theexchangeable cations in bentonite are easily replaceable. For example,ion exchange from Ca⁺ to Na⁺ requires only mixing, and calcium bentonitemay be converted to sodium bentonite by adding sodium bicarbonate toimprove swelling properties. In natural bentonite deposits, Na⁺ isreadily replaced by Ca⁺ and Mg⁺ under leaching conditions. SeeInglethorpe et al., cited above. Table 1 below provides the chemicalcomposition of various calcium bentonites and sodium bentonites.

TABLE 1 X-ray diffraction analysis of bentonite samples Mont- Sam- Na/moril- Gyp- Feld- Cal- ple Ca lonite Mica sum Opal Quartz spar cite 1 Ca76% 0% 10%  6% 4% 4% 0% 2 Na 73% 0% 0% 3% 9% 15%  0% 3 Ca 83% 0% 5% 2%9% 2% 0% 4 Ca 82% 0% 6% 2% 9% 2% 0% 5 Na 82% 0% 0% 0.7%   15%  3% 0% 6Ca 81% 0% 0% 0% 14%  5% 0% 7 Na 78% 0% 7% 0% 14%  1% 0%

Table 2 below shows the Swell Index and specific gravity of variousbentonites in which 3% sodium bicarbonate has been added.

TABLE 2 Swell Index and specific gravity of various bentonites treatedwith sodium bicarbonate Sample 1 2 3 Swell Index, ml/2 g 19 24 20Specific Gravity 2.703 2.701 2.678 % Na₂CO₃ 3% 3% 3%

As described in Example 1 below, Applicants have discovered that when awetted bentonite slurry is combined with a seed in a planting hole, thehydrated microenvironment increases germination rate and totalgermination, and increases seedling growth under drought stressconditions. More robust plant development (e.g., root, stem and leafdevelopment) and increased tolerance to herbivores (snails) was alsoobserved for the bentonite treated seeds relative to control seeds thatwere not treated with bentonite. These improvements in germination andplant growth were observed in seeds treated with bentonite alone, orbentonite in combination with fertilizer (e.g., nitrogen basedfertilizer or nitrogen, phosphorous and potassium based fertilizers,such as MIRACLE-GRO, or organic fertilizers), the plant growth regulatorindole-3-acetic acid (IAA), or the combination of fertilizers and plantgrowth regulators. Thus, Applicants have demonstrated that treatment ofa plant with a water-based bentonite slurry enhances plantgrowth-related traits. A water-based bentonite slurry would also allowfor flowability from an automatic hopper and dispenser to increase theplanting scale.

In certain embodiments, the present invention relates to an agriculturalproduct comprising: a) a slurry comprising bentonite and water; and b) aplant propagative material. In one embodiment, the plant propagativematerial is at least partially in contact with the slurry. For example,the plant propagative material can be placed on top of the slurry.Alternatively, the plant propagative material can be placed below theslurry. In another embodiment, the plant propagative material (e.g., aseed) is submerged in the slurry.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

As used herein, the term “slurry” refers to a thin sloppy fluid mixtureof a pulverized solid with a liquid (usually water). A slurry behaves,in some ways, like a thick fluid and is capable of flowing under gravitybut is also capable of being pumped if not too thick. Slurries of theinstant invention may comprise bentonite and water. The water-basedbentonite slurries of the invention also allow for flowability from anautomatic hopper and dispenser to increase the speed of seed plantingand the planting scale. Use of a hopper applied bentonite allows agrower to apply bentonite slurry only in the parts of a field where itis needed, for example in dry areas. Thus the use of a bentonite slurryis consistent with precision (GPS guided) agricultural “best practices.”This is in contrast to dry seed coating that uses bentonite on allseeds, including in areas where it may not be needed or desirable, suchas flood prone parts of the field. Use of a slurry allows for a discreetapplication of bentonite consistent with modern “precision farming” bestpractices by only treating areas that need treatment

As used herein the term “plant propagative material” refers to all thegenerative part of a plant that may be used for the multiplication ofthe plant. Plant propagative materials include, but are not limited toseeds, roots, tubers, bulbs, rhizomes, leaves, seedlings, transplants,plugs, saplings, and nursery stock of trees and shrubs. In oneembodiment, the plant propagative material is a seed.

As used herein, the term “plug” refers to a seedling grown in a small,individual cell of a tray (for example, a tray made from expandedpolystyrene or polythene) filled with a plant growth medium. Plugs aretypically young plants grown in small, individual cells, fortransplanting into soil or other larger containers. Plugs are generallyraised under controlled conditions for the first few days or weeks ofgrowth. In some embodiments, plugs are treated with a bentonite slurrybefore transplanting, for example, by applying the slurry to the growthmedium. In some embodiments, plugs are treated with a bentonite slurryafter transplanting, for example, by adding the slurry to the plantinghole after the plug is deposited in the soil. Treatment of plugs withbentonite slurry would be especially beneficial under drought conditionsto improve seedling establishment.

Plants that are particularly useful in the present invention includemonocotyledonous and dicotyledonous plants including but not limited tofodder or forage legumes, ornamental plants, food crops, trees, orshrubs selected from Acer spp., Allium spp., Amaranthus spp., Ananascomosus, Apium graveolens, Arachis spp, Asparagus officinalis, Betavulgaris, Brassica spp. (e.g., Brassica napus, Brassica rapa ssp.[canola, oilseed rape, turnip rape]), Camellia sinensis, Canna indica,Cannabis saliva, Capsicum spp., Castanea spp., Cichorium endivia,Citrullus lanatus, Citrus spp., Cocos spp., Coffea spp., Coriandrumsativum, Corylus spp., Crataegus spp., Cucurbita spp., Cucumis spp.,Daucus carota, Fagus spp., Ficus carica, Fragaria spp., Ginkgo biloba,Glycine spp. (e.g., Glycine max, Soja hispida or Soja max), Gossypiumhirsutum, Helianthus spp. (e.g., Helianthus annuus), Hibiscus spp.,Hordeum spp. (e.g., Hordeum vulgare), Ipomoea batatas, Juglans spp.,Lactuca sativa, Linum usitatissimum, Litchi chinensis, Lotus spp., Luffaacutangula, Lupinus spp., Lycopersicon spp. (e.g., Lycopersiconesculenturn, Lycopersicon lycopersicum, Lycopersicon pyriforme), Malusspp., Medicago sativa, Mentha spp., Miscanthus sinensis, Morus nigra,Musa spp., Nicotiana spp., Olea spp., Oryza spp. (e.g., Oryza sativa,Oryza Panicum miliaceum, Panicum virgatum, Passiflora edulis,Petroselinum crispum, Phaseolus spp., Pinus spp., Pistacia vera, Pisumspp., Poa spp., Populus spp., Prunus spp., Pyrus communis, Quercus spp.,Raphanus sativus, Rheum rhabarbarum, Ribes spp., Ricinus communis, Rubusspp., Saccharum spp., Salix sp., Sambucus spp., Secale cereale, Sesamumspp., Sinapis spp., Solanum spp. (e.g., Solanum tuberosum, Solanumintegrifolium or Solanum lycopersicum), Sorghum bicolor, Sorghumhalepense, Spinacia spp., Tamarindus indica, Theobroma cacao, Trifoliumspp., Triticosecale rimpaui, Triticum spp. (e.g., Triticum aestivum,Triticum durum, Triticum turgidum, Triticum hybernum, Triticum macha,Triticum sativum or Triticum vulgare), Vaccinium spp., Vicia spp., Vignaspp., Viola odorata, Vitis spp., and Zea mays. Especially preferred arerice, oilseed rape, canola, soybean, corn (maize), cotton, sugarcane,alfalfa, sorghum, and wheat.

In certain embodiments, the slurry comprises about 1%, 2%, 3%, 4%, 5%,6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%,21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 35%, 40%, 45%, 50%,60%, 70%, 80%, 90%, 95%, 96%, 97%, 98% or 99% (w/w) of bentonite. Insome embodiments the concentration of bentonite in the slurry is atleast about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%,15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%,29%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98% or99% (w/w). Any of these values may be used to define a range for theconcentration of bentonite in the slurry. For example the concentrationof bentonite in the slurry may be from about 1% (w/w) to about 10%(w/w), or from about 10% (w/w) to about 50% (w/w), or from about 25% toabout 75%.

In certain embodiments, the slurry comprises about 10%, 11%, 12%, 13%,14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%,28%, 29%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%,90%, or 95% (w/w) of water. In some embodiments the concentration ofwater in the slurry is at least about 10%, 11%, 12%, 13%, 14%, 15%, 16%,17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%,35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%(w/w). Any of these values may be used to define a range for theconcentration of water in the slurry. For example the concentration ofwater in the slurry may be from about 1% (w/w) to about 10% (w/w), orfrom about 10% (w/w) to about 50% (w/w).

In some embodiments the slurry is a saturated bentonite slurry based onthe Swell Index of the bentonite. As used herein, the term “saturatedslurry” or “saturated bentonite slurry” refers to a slurry whichcontains at least the amount of liquid required for complete saturationof the bentonite as determined by the Swell Index. For example, for abentonite that has a Swell Index of 24 ml/2 g, about 12 ml of fluid areused per gram of bentonite to form a saturated slurry.

In some embodiments the slurry is a supersaturated slurry. As usedherein, the term “supersaturated slurry” or “supersaturated bentoniteslurry” refers to a slurry which contains more than the amount of liquidrequired for complete saturation of the bentonite as determined by theSwell Index. For example, for a bentonite that has a Swell Index of 24ml/2 g, at least about 12 ml of fluid are used per gram of bentonite toform a supersaturated slurry.

In some embodiments, the slurry comprises a bentonite selected from thegroup consisting of a green bentonite, a white bentonite, an off-whitebentonite, a red bentonite, or a brown bentonite.

The slurry comprising bentonite and water may further comprise acompound selected from the group consisting of a fertilizer, a plantgrowth regulator, a fungicide and an insecticide.

In a particular embodiment, the slurry comprising bentonite furthercomprises a compound selected from a fertilizer and a plant growthregulator. A fertilizer may comprise one or more of the elementsimportant for plant growth, including, but not limited to, themacronutrients nitrogen (N), phosphorous (P), and potassium (K); thesecondary macronutrients calcium (Ca), sulfur (S), and magnesium (Mg);and the micronutrients boron (B), chlorine (Cl), manganese (Mn), iron(Fe), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni), and cobalt(Co).

Sources of the elements important for plant growth are well known in theart and are described, for example, in US 2010/0267554. Substances thatmay be added to the slurry to provide nitrogen include, but are notlimited to ammonium sulfate, ammonium nitrate, fish protein digest,ammonium phosphate sulfate, phosphate nitrate, diammonium phosphate,ammoniated single superphosphate, ammoniated triple superphosphate,nitric phosphates, ammonium chloride, calcium nitrate, calciumcyanamide, sodium nitrate, urea, urea-ammonium nitrate solution, nitrateof soda potash, potassium nitrate, and combinations thereof.

Phosphate compounds that may be added to the slurry include, but are notlimited to, mono-potassium phosphate, superphosphate (single/double ortriple), phosphoric acid, ammonium phosphate sulfate, ammonium phosphatenitrate, diammonium phosphate, ammoniated superphosphate (single, doubleor triple), nitric phosphates, potassium pyrophosphates, sodiumpyrophosphate, and combinations thereof.

Potassium compounds that may be added to the slurry include, but are notlimited to, mono-potassium phosphate, potassium chloride, potassiumsulfate, potassium gluconate, sulfate of potash magnesia, potassiumcarbonate, potassium acetate, potassium citrate, potassium hydroxide,potassium manganate, potassium molybdate, potassium thiosulfate,potassium zinc sulfate, and combinations thereof.

Calcium containing materials that that may be added to the slurryinclude, but are not limited to, calcium ammonium nitrate, calciumnitrate, calcium cyanamide, calcium acetate, calcium acetylsalicylate,calcium borate, calcium borogluconate, calcium carbonate, calciumchloride, calcium citrate, calcium ferrous citrate, calciumglycerophosphate, calcium lactate, calcium oxide, calcium pantothenate,calcium propionate, calcium saccharate, calcium sulfate, calciumtartrate, and mixtures thereof.

Magnesium compounds that may be added to the slurry include, but are notlimited to, magnesium sulfate, magnesium oxide, dolomite, magnesiumacetate, magnesium benzoate, magnesium bisulfate, magnesium borate,magnesium chloride, magnesium citrate, magnesium nitrate, magnesiumphosphate, magnesium salicylate, and combinations thereof. Sulfurcompounds that may be added to the slurry include, but are not limitedto, magnesium sulfate, ammonium phosphate sulfate; calcium sulfate,potassium sulfate, sulfuric acid, cobalt sulfate, copper sulfate, ferricsulfate, ferrous sulfate, sulfur, cysteine, methionine, and combinationsthereof.

Zinc containing compounds that may be added to the slurry include, butare not limited to, chelated zinc, zinc sulfate, zinc oxide, zincacetate, zinc benzoate, zinc chloride, zincbis(dimethyldithiocarbamate), zinc citrate, zinc nitrate, zincsalicylate, and combinations thereof.

Iron containing compounds that may be added to the slurry include, butare not limited to, chelated iron, ferric chloride, ferric citrate,ferric fructose, ferric glycerophosphate, ferric nitrate, ferric oxide,ferrous chloride, ferrous citrate, ferrous fumarate, ferrous gluconate,and ferrous succinate, and combinations thereof.

Manganese compounds that may be added to the slurry include, but are notlimited to, manganese sulfate, manganese acetate, manganese chloride,manganese nitrate, manganese phosphate, and combinations thereof.

Cobalt materials that may be added to the slurry include, but are notlimited to, cyanocobalamin, cobaltic acetate, cobaltous chloride,cobaltous oxalate, cobaltous potassium sulfate, cobaltous sulfate, andcombinations thereof.

In certain embodiments, the concentration of the one or more elementsimportant for plant growth in the slurry is about 0.001, 0.005, 0.01,0.05, 0.1, 0.5, 1, 5, 10, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250,275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 600, 700, 800, 900,1000, 2000, 3000, 4000, or 5000 ppm (w/w). In some embodiments, theconcentration of the one or more elements important for plant growth inthe slurry is at least about 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5,10, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350,375, 400, 425, 450, 475, 500, 600, 700, 800, 900, 1000, 2000, 3000,4000, or 5000 ppm (w/w). Any of these values may be used to define arange for the concentration of the element important for plant growth inthe slurry. For example, the concentration of the element important forplant growth in the slurry may range from about 1 ppm (w/w) to about1000 ppm (w/w), or from about 10 ppm (w/w) to about 100 ppm (w/w).

Plant growth regulators that may be added to the slurry comprisingbentonite and water include, but are not limited to, auxins (e.g.,indole-3-acetic acid (IAA), 1-naphthaleneacetic acid (NAA), andindole-3-butyric acid (IBA)), giberellins (e.g., ProGibb 4%),cytokinins, ethylene-related compounds (e.g., ethephon), abscisic acid,brassinosteroids, jasmonates, polyamines, and karrikins. In oneembodiment of the invention, the plant growth regulator is IAA.

As used herein, the term “ethylene-related compounds” refers tocompounds that release ethylene upon application to the plant (e.g.ethephon) or compounds that regulate ethylene sensitivity (e.g. silverthiosulfate (STS)).

Additional compounds that may be added to the slurry comprisingbentonite and water include, but are not limited to, amino acids,peptides, proteins, and gene regulators (e.g. transcription andtranslation regulators).

In certain embodiments, the concentration of the plant growth regulatorin the slurry is about 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 25,50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400,425, 450, 475, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, or 5000ppm. In some embodiments, the concentration of the plant growthregulator in the slurry is at least about 0.001, 0.005, 0.01, 0.05, 0.1,0.5, 1, 5, 10, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300,325, 350, 375, 400, 425, 450, 475, 500, 600, 700, 800, 900, 1000, 2000,3000, 4000, or 5000 ppm. Any of these values may be used to define arange for the concentration of the plant growth regulator in the slurry.For example, the concentration of the plant growth regulator in theslurry may range from about 10 ppm to about 500 ppm, from about 1 ppm toabout 25 ppm, or from about 0.1 ppm to about 10 ppm.

Fungicides that may be added to the slurry comprising bentonite andwater include, but are not limited to, trifloxystrobin, metalaxyl,tebuconazole, imazalil, pyraclostrobin and ipconazole.

Insecticides that may be added to the slurry comprising bentonite andwater include, but are not limited to, imidacloprid (e.g., MACHO 600ST,GAUCHO 600 FS), clothianidin (e.g., BELAY, PONCHO), terbufos (e.g.,COUNTER), thiamethoxam (e.g., CRUISER), clove, thyme and cinnamon oil(e.g., ECOTROL), tefluthrin (e.g., FORCE), chlorethoxyfos (e.g.,FORTRESS), permethrin, and carboxin.

Microorganisms that enhance plant growth may also be added to theslurry. For example, Rhizobium inoculant may be added to the slurry toenhance nitrogen fixation in legumes.

The slurries may be prepared by adding powdered forms of bentonite towater and then mixing by hand or with an automated mixer. In someembodiments, additional compounds such as fertilizers, plant growthregulators, insecticides, and fungicides as described above may be mixedwith the water before adding the powdered bentonite. In otherembodiments, the powdered bentonite is first mixed with water and thenadditional compounds such as fertilizers, plant growth regulators,insecticides, and fungicides as described above may be added. Methods ofpreparing water-based slurries from clay powders are known in the artand are described, for example, in U.S. Pat. No. 8,691,052.

In certain aspects, the present invention relates to a method ofenhancing a growth-related trait in a plant propagative materialrelative to a control plant propagative material, comprising applying aslurry comprising bentonite and water to a plant growth medium; andcontacting a plant propagative material with the slurry in the plantgrowth medium, wherein a growth-related trait of the plant propagativematerial is enhanced relative to a control plant propagative materialthat is not treated with the slurry. In particular embodiments, thegrowth-related trait is enhanced under conditions of environmentalstress, for example, drought conditions. In particular embodiments, thegrowth-related trait is enhanced in a crop that is not irrigated. Inanother embodiment, the growth-related trait is enhanced in a crop thatrelies on natural sources of water, e.g., rain.

In one embodiment, the slurry comprising bentonite and water may beapplied using an automatic hopper and dispenser, which increases thespeed of planting. In one embodiment, the slurry may be dispensed usingmechanical methods, compression methods, air pressure methods, jetstream methods, gravity methods, centrifugal methods, metered pumpmethods, hydraulic methods, or other methods. In some embodiments, anapplicator which is custom designed for application of the slurry may beused. For example, the slurry comprising bentonite and water may beapplied using a custom designed applicator, for example, for bentoniteembedded planting plugs, which increases the speed of planting.

The growth-related traits that may be enhanced by the methods of thepresent invention include, but are not limited to, total seedgermination, rate of seed germination, plant biomass, disease tolerance,insect tolerance, herbivore tolerance (for example, tolerance to feedingby animals such as snails, rabbits, deer or groundhogs), droughttolerance, heat tolerance, cold tolerance, salinity tolerance, toleranceto heavy metals, total yield, seed yield, flowering time (e.g. earlyflowering time), root growth, early vigor, plant biomass, plant size,total plant dry weight, above-ground dry weight, above-ground freshweight, leaf area, stem volume, plant height, rosette diameter, leaflength, root length, root mass, tiller number, and leaf number.

In particular embodiments, the growth-related trait is selected from thegroup consisting of total seed germination, rate of seed germination,plant biomass, insect tolerance, early flowering time, herbivoretolerance, and drought tolerance.

As used herein, the term “biomass” refers to the total weight of aplant. Within the definition of biomass, a distinction may be madebetween the biomass of one or more parts of a plant, which may includeany one or more of the following: aboveground parts including, but notlimited to, shoot biomass, seed biomass, leaf biomass; abovegroundharvestable parts including, but not limited to, shoot biomass, seedbiomass, leaf biomass; parts below ground, including, but not limitedto, root biomass, tubers, bulbs; harvestable parts below ground,including, but not limited to, root biomass, tubers, bulbs; harvestableparts partially below ground including, but not limited to, beets andother hypocotyl areas of a plant, rhizomes, stolons or creepingrootstalks; vegetative biomass including, but not limited to, rootbiomass, shoot biomass; reproductive organs; and propagules including,but not limited to, seeds.

As used herein, the term “early flowering time” refers to a plant whichbegins to flower earlier than a control plant. Thus, this term refers toplants that show an earlier start of flowering. Flowering time of plantscan be assessed by counting the number of days (“time to flower”)between sowing and the emergence of a first inflorescence. The“flowering time” of a plant can for instance be determined using themethod as described in WO07/093444, the entire contents of which areincorporated herein by reference.

As used herein, the term “drought conditions” refers to any stress whichleads to a lack of water content in plants, a lack of water availabilityto plants, a lack of water uptake potential in plants, or a reduction inthe water supply to plants. Specifically, a “drought” refers to adeficiency of precipitation resulting from a short term or long-termweather pattern. Drought conditions are determined easily by one ofordinary skill in the art. For example, the Palmer Drought SeverityIndex (PDSI), which is a measure of soil moisture, the Crop MoistureIndex (CMI), and the Z index can be used to determine droughtconditions.

Growth-related traits may be enhanced using the methods of the presentinvention. For example, in some embodiments, any of the growth-relatedtraits described herein may be increased by at least about 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100,150, 200, 300, 400, 500, 600, 700, 800, 900 or 1000% in a plantpropagative material to which a slurry comprising bentonite and waterhas been applied relative to a control plant propagative material towhich a bentonite/water slurry has not been applied.

For example, in some embodiments, total seed germination may beincreased by at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, or 95% in a plant propagative material towhich a slurry comprising bentonite and water has been applied relativeto a control plant propagative material to which a bentonite/waterslurry has not been applied. In one embodiment, total seed germinationmay be enhanced 2-fold in a plant propagative material to which a slurrycomprising bentonite and water has been applied, as compared to acontrol plant propagative material to which a bentonite/water slurry hasnot been applied. In one embodiment, total seed germination may beenhanced 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or10-fold in a plant propagative material to which a slurry comprisingbentonite and water has been applied, as compared to a control plantpropagative material to which a bentonite/water slurry has not beenapplied.

In a particular embodiment, the total seed germination is increased byat least 3-fold (for example, from 33% germination to at least 99%germination) under drought conditions. This level of increase in totalseed germination under drought conditions can prevent crop failure dueto drought and eliminate the need for replanting.

In another embodiment, the rate of seed germination may be decreased by1 day in a plant propagative material to which a slurry comprisingbentonite and water has been applied, as compared to a control plantpropagative material to which a bentonite/water slurry has not beenapplied. In one embodiment, the rate of seed germination may bedecreased by 0.5 days, 1 day, 1.5 days, 2 days, 3 days, 4 days, 5 days,6 days, 7 days, 8 days, 9 days, 10 days or 14 days in a plantpropagative material to which a slurry comprising bentonite and waterhas been applied, as compared to a control plant propagative material towhich a bentonite/water slurry has not been applied.

In another embodiment, the percentage of seed germination may beincreased by 10% in a plant propagative material to which a slurrycomprising bentonite and water has been applied, as compared to acontrol plant propagative material to which a bentonite/water slurry hasnot been applied. In one embodiment, the percentage of seed germinationmay be increased by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%,60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% in a plant propagativematerial to which a slurry comprising bentonite and water has beenapplied, as compared to a control plant propagative material to which abentonite/water slurry has not been applied.

In another embodiment, plant biomass may be enhanced by at least about5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,or 95% in a plant propagative material to which a slurry comprisingbentonite and water has been applied, as compared to a control plantpropagative material to which a bentonite/water slurry has not beenapplied. In some embodiments, plant biomass may be enhanced by at leastabout 2-fold in a plant propagative material to which a slurrycomprising bentonite and water has been applied, as compared to acontrol plant propagative material to which a bentonite/water slurry hasnot been applied. In one embodiment, plant biomass may be enhanced1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-foldor 10-fold in a plant propagative material to which a slurry comprisingbentonite and water has been applied, as compared to a control plantpropagative material to which a bentonite/water slurry has not beenapplied.

In some embodiments, insect tolerance may be enhanced by at least about5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,or 95% in a plant propagative material to which a slurry comprisingbentonite and water has been applied, as compared to a control plantpropagative material to which a bentonite/water slurry has not beenapplied. In some embodiments, insect tolerance may be enhanced 2-fold ina plant propagative material to which a slurry comprising bentonite andwater has been applied, as compared to a control plant propagativematerial to which a bentonite/water slurry has not been applied. In oneembodiment, insect tolerance may be enhanced 1.5-fold, 2-fold, 3-fold,4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold in a plantpropagative material to which a slurry comprising bentonite and waterhas been applied, as compared to a control plant propagative material towhich a bentonite/water slurry has not been applied.

Insect tolerance, disease tolerance and environmental stress tolerance(e.g., drought tolerance) may be measured by measuring any of the growthrelated traits described herein. For example, drought tolerance may bedetermined by measuring percent germination, rate of germination, plantbiomass, yield, or seed yield under drought conditions. The insecttolerance, disease tolerance, or environmental stress tolerance may bequantified by measuring the growth-related trait under the appropriateconditions. For example, a plant propagative material treated with aslurry comprising bentonite and water that exhibited a 10% increase inyield relative to a plant propagative material that was not treated withthe slurry would be determined to exhibit a 10% increase in droughttolerance. As another example, a plant propagative material treated witha slurry comprising bentonite and water that exhibited a 10% increase inthe rate of leaf out, as compared to a plant propagative material thatwas not treated with the slurry would be determined to exhibit a 10%increase in insect tolerance. A plant propagative material withincreased rate of leaf out is more resistant to insect infestation orattack.

In some embodiments, disease tolerance or herbivore tolerance may beincreased by at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, or 95% in a plant propagative material towhich a slurry comprising bentonite and water has been applied relativeto a control plant propagative material to which a bentonite/waterslurry has not been applied. In another embodiment, disease tolerance orherbivore tolerance may be enhanced 2-fold in a plant propagativematerial to which a slurry comprising bentonite and water has beenapplied, as compared to a control plant propagative material to which abentonite/water slurry has not been applied. In one embodiment, diseasetolerance or herbivore tolerance may be enhanced 1.5-fold, 2-fold,3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold in aplant propagative material to which a slurry comprising bentonite andwater has been applied, as compared to a control plant propagativematerial to which a bentonite/water slurry has not been applied.

In some embodiments, drought tolerance may be increased by at leastabout 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,90, or 95% in a plant propagative material to which a slurry comprisingbentonite and water has been applied relative to a control plantpropagative material to which a bentonite/water slurry has not beenapplied. In some embodiments, drought tolerance may be enhanced 2-foldin a plant propagative material to which a slurry comprising bentoniteand water has been applied, as compared to a control plant propagativematerial to which a bentonite/water slurry has not been applied. In oneembodiment, drought tolerance may be enhanced 1.5-fold, 2-fold, 3-fold,4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold in a plantpropagative material to which a slurry comprising bentonite and waterhas been applied, as compared to a control plant propagative material towhich a bentonite/water slurry has not been applied.

In some embodiments, heat tolerance or cold tolerance may be increasedby at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, or 95% in a plant propagative material to which a slurrycomprising bentonite and water has been applied relative to a controlplant propagative material to which a bentonite/water slurry has notbeen applied. In some embodiments, heat tolerance or cold tolerance maybe enhanced 2-fold in a plant propagative material to which a slurrycomprising bentonite and water has been applied, as compared to acontrol plant propagative material to which a bentonite/water slurry hasnot been applied. In one embodiment, heat tolerance or cold tolerancemay be enhanced 1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold,7-fold, 8-fold, 9-fold or 10-fold in a plant propagative material towhich a slurry comprising bentonite and water has been applied, ascompared to a control plant propagative material to which abentonite/water slurry has not been applied.

In some embodiments, salinity tolerance or tolerance to heavy metals maybe increased by at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,55, 60, 65, 70, 75, 80, 85, 90, or 95% in a plant propagative materialto which a slurry comprising bentonite and water has been appliedrelative to a control plant propagative material to which abentonite/water slurry has not been applied. In some embodiments,salinity tolerance or tolerance to heavy metals may be enhanced 2-foldin a plant propagative material to which a slurry comprising bentoniteand water has been applied, as compared to a control plant propagativematerial to which a bentonite/water slurry has not been applied. In oneembodiment, salinity tolerance or tolerance to heavy metals may beenhanced 1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold,8-fold, 9-fold or 10-fold in a plant propagative material to which aslurry comprising bentonite and water has been applied, as compared to acontrol plant propagative material to which a bentonite/water slurry hasnot been applied. Salinity tolerance or tolerance to heavy metals may bedetermined using standard methods in the art. For example, salinity maybe determined by measuring the exchange of cations, e.g., calcic tosodic.

In some embodiments, total yield may be increased by at least about 5,10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or95% in a plant propagative material to which a slurry comprisingbentonite and water has been applied relative to a control plantpropagative material to which a bentonite/water slurry has not beenapplied. In some embodiments, total yield may be enhanced 2-fold in aplant propagative material to which a slurry comprising bentonite andwater has been applied, as compared to a control plant propagativematerial to which a bentonite/water slurry has not been applied. In oneembodiment, total yield may be enhanced 1.5-fold, 2-fold, 3-fold,4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold in a plantpropagative material to which a slurry comprising bentonite and waterhas been applied, as compared to a control plant propagative material towhich a bentonite/water slurry has not been applied. In one embodimentof the invention, at least 75% of the total number of seeds to which abentonite/water slurry are applied germinate. In another embodiment, atleast 80%, 85%, 90%, 95%, or 100% of the total number of seeds to whicha bentonite/water slurry are applied germinate.

In some embodiments, root growth, early vigor, plant size, total plantdry weight, above-ground dry weight, above-ground fresh weight, leafarea, stem volume, plant height, rosette diameter, leaf length, rootlength, root mass, tiller number, or leaf number may be increased by atleast about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75,80, 85, 90, or 95% in a plant propagative material to which a slurrycomprising bentonite and water has been applied relative to a controlplant propagative material to which a bentonite/water slurry has notbeen applied. In some embodiments, root growth, early vigor, plant size,total plant dry weight, above-ground dry weight, above-ground freshweight, leaf area, stem volume, plant height, rosette diameter, leaflength, root length, root mass, tiller number, or leaf number may beenhanced 2-fold in a plant propagative material to which a slurrycomprising bentonite and water has been applied, as compared to acontrol plant propagative material to which a bentonite/water slurry hasnot been applied. In one embodiment, root growth, early vigor, plantsize, total plant dry weight, above-ground dry weight, above-groundfresh weight, leaf area, stem volume, plant height, rosette diameter,leaf length, root length, root mass, tiller number, or leaf number maybe enhanced 1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold,8-fold, 9-fold or 10-fold in a plant propagative material to which aslurry comprising bentonite and water has been applied, as compared to acontrol plant propagative material to which a bentonite/water slurry hasnot been applied.

Generally, an “enhanced growth-related trait” or an “increase in agrowth-related trait” refers to a level of the trait in a test plantpropagative material that is greater than the standard error of theassay employed to assess the level of the trait, and is preferably atleast twice, and more preferably three, four, five or ten times thelevel of the trait in a control sample (e.g., sample of a plantpropagative material that has not been contacted with a bentonite/waterslurry) and preferably, the average expression level of the trait inseveral control samples.

Values and ranges included and/or intermediate within the ranges setforth herein are also intended to be within the scope of the presentdisclosure. Ranges having values recited herein as an upper or lowerlimit are also intended to be within the scope of the presentdisclosure.

Unlike seed coating, the water-based slurry comprising bentoniteimmediately introduces a long lasting hydrated microcosm that inducesseed germination. For example, the slurry provides a hydratedmicroenvironment to the seed that keeps the seed shell moist andpromotes water absorption into the shell. This in turn allows the shellto swell and eventually crack and initiate germination. Intermittentdrought stress is mitigated, as the slurry volume maintains a hydratedenvironment to promote seed shell swelling and germination. Bentonite isextremely hygroscopic and will not release water easily to thesurrounding soil. Plant propagative materials, however, such as seeds,are porous. Thus, when surrounded by a bentonite slurry of theinvention, the bentonite provides a hydrated microcosm for the plantpropagative material, and capillary action draws water into the seedshell, which induces seed germination. Once the seed shell has swollenand cracked, plant growth regulators and fertilizer in the slurry canenhance germination and rooting activity and expedite emergence of theseedling from the soil and early growth of the developing seedling. Inone embodiment, the slurry comprising bentonite and water, along with aplant propagative material (for example, a seed) may be applied to aplant growth medium (for example, a soil) using an automatic hopper anddispenser, which increases the speed of planting.

In certain embodiments, the growth related trait is enhanced underunfavorable environmental conditions, including, but not limited to,drought conditions, high salinity conditions, cold stress conditions andheat stress conditions. As used herein, the term “drought conditions”refer to conditions under which a region receives a deficiency in itswater supply, whether atmospheric, surface, or ground water. Due to thehydrated microenvironment that the slurry provides, the slurry isparticularly well suited for enhancing growth-related traits underdrought conditions or under conditions of high salinity. The slurry mayalso enhance growth-related traits under other environmental stressconditions, such as high or low temperature conditions. For example, thepositive effects of the slurry on germination and growth of the seedlingmay counteract negative effects caused by unfavorable temperatures.

In some embodiments, the slurry is added to the plant growth mediumbefore planting the plant propagative material. For example, in someembodiments, the slurry is applied to the plant growth medium (forexample, a soil) and the plant propagative material (for example, aseed) is then introduced into the plant growth medium after the slurryhas been applied. In some embodiments, the plant propagative material(for example, a seed) is placed in direct contact with the slurry whichhas been added to the plant growth medium (for example, a soil). Forexample, for seed planting, a drop of the slurry may be introduced intothe planting hole and the seed may then be placed in contact with theslurry. The hole containing the seed and the slurry may then be coveredwith additional plant growth medium.

In one embodiment, the slurry comprising bentonite and water, along witha plant propagative material (for example, a seed) may be applied to aplant growth medium (for example, a soil) using an automatic hopper anddispenser, which increases the speed of planting. In one embodiment, theslurry and the plant propagative material may be applied to a plantgrowth medium at the same time using an automatic hopper and dispenser.In another embodiment, the slurry and the plant propagative material maybe applied sequentially to a plant growth medium using an automatichopper and dispenser. For example, an automatic hopper and dispenser maybe used to first apply the slurry, followed by the plant propagativematerial. Alternatively, an automatic hopper and dispenser may be usedto first apply the seed, followed by the slurry.

For transplanting (e.g., vegetable transplants, flower transplants,trees, or shrubs) the slurry may be applied to a hole in the plantgrowth medium (e.g., soil) and the transplant may then be applied to thehole containing the slurry. The slurry may also be mixed into the plantgrowth medium before the plant propagative material is planted. Forexample, for field production, the slurry may be broadcast in the fieldand mixed into the soil before seeds or transplants are planted. Inother embodiments, the slurry is not mixed into the plant growth mediumbefore the plant propagative material is introduced into the medium. Theslurry may be applied to the plant growth medium manually or usingequipment such as a spreader or planter, followed by application of theplant propagative material.

In some embodiments, the slurry is applied to discrete areas of a fieldin which the plant propagative material will be planted, such as aplanting hole or a planting row, and is not broadcast across the field.Discrete application of the slurry to the planting area reduces theamount of slurry needed and prevents changes to the composition of thesoil that may occur with broadcasting of bentonite. In certainembodiments, the slurry is applied to the planting medium at a rate ofless than about 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100, 90,80, 70, 60, 50, 40, 30, 20 or 10 kg/acre. Any of these values may beused to define a range for the amount of the slurry that is applied tothe field. For example, the slurry may be applied to the field at a ratefrom about 100 to about 1000 kg/acre, from about 50 to about 500kg/acre, or from about 10 to about 100 kg/acre.

In certain embodiments, the slurry is applied to less than 90%, 80%,70%, 60%, 50%, 40%, 30%, 20%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%of the surface area of the plant growth medium, for example the surfacearea of a field.

In some embodiments the slurry is applied to the plant propagativematerial before the plant propagative material is introduced into theplant growth medium. For example, seeds may be mixed with the slurry toform a seed/slurry mixture, and this mixture may be applied to the plantgrowth medium. In one embodiment, the seed/slurry mixture may be appliedto the plant growth medium using an automatic hopper and dispenser. Insome embodiments, the slurry is applied to the roots of a seedling ortransplant, for example by dipping or submerging the roots of the plantinto the slurry, and the treated seedling or transplant is thenintroduced into the plant growth medium. In some embodiments, forexample for gardening or landscaping applications, the mixture of theslurry and plant propagative material is applied to the plant growthmedium manually. In some embodiments, for example, for large-scale cropproduction, the mixture of the slurry and the plant propagative materialis applied in the field using commercially available planters orspreaders, such as automated transplanters used for vegetable productionor seed planters used in no-till farming systems. For automated seedplanting, a mixture of seed and slurry may be added to the seed hopperof a seed planter.

In one embodiment, the slurry comprising bentonite and water may beapplied using an automatic hopper and dispenser, which increases thespeed of planting. In one embodiment, the slurry may be dispensed usingmechanical methods, compression methods, air pressure methods, jetstream methods, gravity methods, centrifugal methods, metered pumpmethods, hydraulic methods, or other methods. In some embodiments, anapplicator which is custom designed for application of the slurry may beused. For example, the slurry comprising bentonite and water may beapplied using a custom designed applicator, for example, for bentoniteembedded planting plugs, which increases the speed of planting.

The slurry comprising bentonite and water may also be applied using anindustrial fertilizer applicator under intermittent pressure to applydiscrete amounts of the slurry to the planting hole, or under constantpressure to apply a stream of the slurry to a seed row. Fertilizerapplicators are commercially available, for example, from John Deere(Moline, Ill.).

The slurry or seed/slurry mixture may also be applied to a plant growthmedium contained in a pot, for example a pot comprising peat moss or asynthetic plant growth medium. In some embodiments, the slurrycomprising bentonite and water is incorporated into a preformed plantingcontainer for plug production comprising peat moss and optionally otherplant growth medium. Preformed planting containers comprising peat mossfor plug production are commercially available, for example, fromGrow-Tech LLC (South Portland, Me.).

As used herein, the term “plant growth medium” refers to a medium thatis capable of supporting a plant, including but not limited to, fieldsoil, potting soil, perlite, vermiculite, peat moss, mineral wool,compost, or mixtures thereof. In one embodiment, the plant growth mediumis soil. In another embodiment, the plant growth medium is field soil.

In some embodiments, the slurry comprising bentonite and water isapplied to a plug, e.g., a seedling grown in a tray (e.g., an expandedpolystyrene or polythene tray) filled with growth medium. The slurry maybe applied to the plug by dipping the roots of the plug into a bentoniteslurry of the invention or by flooding or soaking the tray in which theplug is grown with the bentonite slurry. Once the plug is treated withthe bentonite slurry of the invention, the treated plugs may be plantedin a field or in a controlled growth environment. In another embodiment,the slurry comprising bentonite and water is applied to a plug, e.g., aseed grown in a tray (e.g., an expanded polystyrene or polythene tray)filled with growth medium. Once the plug is treated with the bentoniteslurry of the invention, the treated plugs may be planted in a field orin a controlled growth environment. Alternatively, a plant growthmedium, such as a seed, may be inserted mechanically into a bentonitepeat (or peat similar) plug, and then planted in soil or a pot manuallyor using machines.

In a particular embodiment, the treated plug is grown under broadspectrum LED lighting using a hydroponic system. In a preferredembodiment, the plug is an herb, for example, basil, parsley, orcilantro. In some embodiments, the seed planted into the tray forproduction of the plug may also be treated with slurry by the methodsdescribed herein. For example, the slurry may be added to the growthmedium before planting the seed, or the seed may be treated with theslurry before planting.

The slurry of the present invention may also be used in landreclamation, for example, after afforestation, to improve the survivaland growth of plants such as grass or trees under unfavorableenvironmental conditions such as poor soil quality, flooding or drought.Accordingly, in one embodiment, the invention provides methods forpromoting reforestation comprising applying a slurry comprisingbentonite and water to the soil. For reforestation, the slurrycomprising bentonite and water may be applied by dipping the roots of atree sapling or grass into the slurry before planting. Alternatively,the slurry comprising bentonite and water may be applied to a plantgrowth medium, followed by introduction of a plant propagative materialinto the plant growth medium containing the slurry.

In some aspects, the present invention relates to methods of remediatingsoil contaminated by heavy metal ions or other pollutants by applyingany of the aforementioned slurries comprising water and bentonite to thecontaminated soil.

In some embodiments, the bentonite may be applied to discrete areas ofthe plant growth medium without formation of a slurry. For example, thebentonite may be applied to discrete areas of the plant growth medium(e.g., a planting hole or planting row) in the form of a dry powder.Water or a fertilizer may then be added to the plant growth medium tohydrate the bentonite.

In some aspects, the present invention relates to a method of enhancinga growth-related trait in a plant propagative material relative to acontrol plant propagative material, comprising a) applying bentonite toa discrete area of a plant growth medium; and b) introducing the plantpropagative material into the discrete area of the plant growth mediumcontaining the bentonite,

wherein the growth-related trait of the plant propagative material isenhanced relative to a control plant propagative material that is nottreated with the bentonite.

Any of the methods described above for applying a slurry to the plantgrowth medium may also be used to apply the dry bentonite to a discretearea of the plant growth medium.

In certain embodiments, the bentonite is applied to the planting mediumat a rate of less than about 1000, 900, 800, 700, 600, 500, 400, 300,200, 100, 90, 80, 70, 60, 50, 40, 30, 20 or 10 kg/acre. Any of thesevalues may be used to define a range for the amount of the slurry thatis applied to the field. For example, the slurry may be applied to thefield at a rate from about 100 to about 1000 kg/acre, from about 50 toabout 500 kg/acre, or from about 10 to about 100 kg/acre.

In certain embodiments, the bentonite is applied to less than 90%, 80%,70%, 60%, 50%, 40%, 30%, 20%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%of the surface area of the plant growth medium, for example the surfacearea of a field.

The present invention is further defined in the following Example. Itshould be understood that this Example, while indicating preferredembodiments of the invention, is given by way of illustration only.

EXAMPLES Example 1—Effect of Bentonite, Indole-3-Acetic Acid (IAA) andFertilizer on Sunflower Seed Germination and Growth Under Water Stress

Sunflower seeds (cultivar ‘Mammoth’, W. Atlee Burpee & Co., Warminster,Pa.) of equal size and uniformity were chosen. Seeds with cracks werediscarded. The seeds were planted into uniform store bought potting soilwhich did not contain growth promoters.

Seven treatment groups were evaluated:1) control, potting soil only without bentonite;2) green bentonite slurry;3) white bentonite slurry;4) green bentonite/IAA (indole-3-acetic acid) slurry;5) white bentonite/IAA slurry;6) green bentonite/fertilizer slurry;7) white bentonite/fertilizer slurry.

Treatment groups 1-5 contained 6 pots each with one seed per pot.Treatment groups 6 and 7 contained 3 pots each with one seed per pot.White bentonite and green bentonite slurries (treatment groups 2 and 3)were prepared with water. Sufficient water was added to form asupersaturated slurry. For example, more than 24 ml of water was addedper 2 grams of bentonite, and the bentonite was allowed to saturate over12 hours with periodic stirring. After 12 hours, the slurry had settledto the bottom of the container with excess water pooled on top of theslurry. The excess water was poured off. The bentonite/IAA slurries(treatment groups 4 and 5) were prepared as described above, except thatIAA powder was added to the bentonite before adding the water to producea final concentration of 200 ppm IAA in the slurry. Thebentonite/fertilizer slurry was prepared as described above except thatfertilizer solution was mixed with the bentonite instead of water. Thefertilizer used was MIRACLE-GRO (Scotts Miracle-Gro Company, Marysville,Ohio) at the manufacturer's recommended concentration of 1 tablespoonMIRACLE-GRO fertilizer per gallon of water. The concentration of plantnutrients in the diluted fertilizer solution is shown in Table 1 below.

TABLE 3 Concentration of plant nutrients in fertilizer solution added toslurry Nutrient Concentration (ppm) Nitrogen 937.5 Potassium 312.5Phosphorous 625 Boron 0.78 Copper 2.73 Iron 5.85 Manganese 1.95Molybdenum 0.02 Zinc 2.34

Holes were made in the potting soil at equal measured depths and a drop(about 2 ml) of the slurry at least twice the size of the seed was addedto the planting hole with a syringe. See FIG. 1. Each sunflower seed wasembedded into the middle of the drop of slurry and covered with soil.

The seedlings were grown under water stress conditions to determine theeffect of the bentonite slurry during drought stress. After planting,the potting soil was watered uniformly until complete saturation andthen was not watered for four days until the soil was completely dry.After four days the soil was watered lightly and then allowed to drycompletely with no watering for another 4 days. This 4 day wateringcycle of light watering followed by 4 days of no watering was repeatedthroughout the course of the study.

Results

Bentonite had a positive effect on seed germination and plant growthunder water stress conditions.

For example, the seeds treated with bentonite, either alone or incombination with fertilizer or IAA, germinated in 5-7 days and exhibited100% germination, while the control seeds which were not treated withbentonite germinated in 12-15 days and exhibited only 33% germination.Thus the bentonite treatment increased both the rate of germination andthe total percentage of germination under water stress conditions.

In addition, plants treated with bentonite exhibited accelerated growth,were larger, and had more robust stem and leaf development relative tothe control plants. For example, some of the seedlings emerged from thesoil but failed to “leaf out”, i.e., develop cotyledons and/or trueleaves. As shown in Table 2 below, the plants treated with bentoniteexhibited a higher percentage of leaf out than the control plants. Itwas also observed that the control plants were more susceptible todamage by snails, possibly due to their slower growth rates. Thus themore rapid early growth of seeds treated with bentonite can also improvetolerance to herbivory by animals and insects that prey on newlygerminating seeds.

TABLE 4 Germination and growth of sunflower seedlings with our withouttreatment with bentonite, IAA, or fertilizer. Treatment groups 1-7 aredescribed above. Treatment Group 1 2 3 4 5 6 7 Percent total 33% 100%100% 100% 100% 100% 100% germination Days to 7-12 5-7 5-7 5-7 5-7 5-75-7 germination Percent leaf out 33% 100%  50% 100%  83% 100% 100%

Example 2—Effect of Bentonite on Sunflower Seed Germination and SoilMoisture Retention

Sunflower seeds (cultivar ‘Mammoth’, W. Atlee Burpee & Co., Warminster,Pa.) of equal size and uniformity were chosen. Seeds with cracks werediscarded. The seeds were planted into uniform store bought potting soilwhich did not contain growth promoters. Two treatment groups wereevaluated:

1) potting soil only without bentonite (control); and

2) bentonite slurry.

The bentonite slurry was prepared with distilled water as describedabove in Example 1. No fertilizer or growth hormone was added to theslurry. The seeds were planted into trays containing 8 pots (see FIGS.6A and 6B). Each pot was filled halfway with potting soil, anindentation was made in the potting soil, and the indentation was filledwith approximately 1 ml of bentonite slurry. One seed was then insertedinto the bentonite slurry, and the pots were filled with potting soiland watered to saturation. The seedlings were grown under drought stressconditions by watering the pots every four days and allowing the pottingsoil to dry thoroughly between waterings. The seedlings were grownindoors with exposure to natural light. Germination was measured dailyuntil all seeds had germinated. As shown in Table 5 below, seeds treatedwith the bentonite slurry exhibited an average total percent germinationof 85% under drought stress conditions compared to an average totalpercent germination of 36% for the seeds that were not treated withbentonite.

TABLE 5 Percent germination of sunflower seeds with and withoutbentonite. Each replicate contained four pots with bentonite slurry andsoil and four pots with soil alone (control). % germination Replicatebentonite + soil soil 1 83% 33% 2 100%  25% 3 50% 33% 4 75% 25% 5 100% 50% 6 75% 25% 7 100%  25% 8 83% 25% 9 100%  50% 10 100%  25% 11 75% 25%12 83% 33% 13 100%  50% 14 83% 33% 15 100%  25% 16 75% 25% 17 100%  25%18 100%  75% 19 75% 25% 20 75% 25% 21 100%  20% 22 100%  50% 23 75% 25%24 100%  75% 25 50% 50% 26 75% 25% 27 100%  50% 28 50% 50% 29 100%  50%30 75% 25% Average % Germination 85% 36% Number of containers n = 120 n= 120

In addition, the seeds treated with bentonite slurry germinated morerapidly than seeds that were not treated with bentonite. For example, asshown in Table 6 below, 97% of the replicates treated with bentoniteslurry had at least one seed that germinated in 5-7 days, while only 7%of the replicates containing control seeds grown in soil alone had atleast one seed that germinated in this time period. Thus treatment withbentonite slurry increased both total germination and the rate ofgermination under drought stress conditions.

TABLE 6 Days to germination of sunflower seeds with and withoutbentonite. Each replicate contained four pots with bentonite slurry andsoil and four pots with soil alone (control). Percentages reflect thenumber of replicates that contained at least one seed that germinatedwithin the indicated time period. Time to germinate Replicate 5-7 days8-12 days > than 12 1 x + 2 x + 3 x + 4 x x + + 5 x + 6 x + 7 x + 8x + + 9 x x + 10 x + 11 x + 12 x + 13 x + 14 x x + + 15 x + 16 x + 17x + 18 x + + 19 x + + 20 x x + 21 x + + 22 x + 23 x + 24 x + 25 x x + 26x + 27 x + 28 x + x + 29 x + + 30 x + + bentonite + bentonite +bentonite + soil: 97% soil: 23% soil: 0% soil alone: 7% soil alone: 80%soil alone: 43% “x” indicates bentonite + soil and “+” indicates soilalone (control).

Example 3—Moisture Retention of a Bentonite Slurry Plug in PottingMedium

The moisture retention abilities of a bentonite slurry plug embedded inpotting soil was determined. Three treatment groups were evaluated:

1. Wetted soil+bentonite slurry;

2. Wetted soil without bentonite (control); and

3. Non-wetted soil without bentonite (control).

The bentonite slurry was prepared with distilled water as describedabove in Example 1. Four holes were made in the bottom of a plastic cupfor drainage. Screened commercially available potting soil that did notcontain vermiculite was used for all treatment groups. For the wettedsoil+bentonite slurry treatment group, the plastic cups were filledapproximately halfway with potting soil, and an indentation was made inthe potting soil. The indentation was filled with approximately 10 ml ofbentonite slurry to form a bentonite slurry plug embedded in the pottingsoil. See FIG. 7. The cup was then filled with potting soil and wateredto saturation. For the control groups, cups were filled with pottingsoil without adding bentonite slurry. For the wetted soil control, cupswere watered to saturation. No water was added to the non-wetted soilcontrol. The cups were not watered again throughout the course of theexperiment. The cups were stored indoors at room temperature. Thepercent soil moisture was measured daily for 30 days using an HSM50 soilmoisture meter (Omega, Stamford, Conn.). For the bentonite slurry+soiltreatment group, the soil moisture meter probe was inserted into thebentonite slurry plug for measurement of moisture levels. As shown inTables 7 and 8 below, the bentonite slurry embedded in wetted pottingsoil maintained a higher moisture content than wetted soil alone or thenon-wetted potting soil control throughout the course of the experiment.These results demonstrate the water retention properties of thebentonite slurry.

TABLE 7 Moisture retention in potting medium with our without bentonite.Values are percent soil moisture and are an average of threemeasurements. Non Wetted Wetted Wetted Day Soil Control Bentonite + SoilSoil 1 9.7 22.7 22.3 2 9.6 22.6 22.1 3 9.5 22.5 21.7 4 9.4 22.2 21.3 59.3 22.0 20.3 6 9.1 21.7 19.8 7 9.0 21.4 19.4 8 8.7 21.2 19.1 9 8.8 20.918.6 10 8.4 20.7 17.7 11 8.2 20.6 17.2 12 7.9 20.4 17.1 13 7.9 20.3 16.914 7.6 20.0 16.4 15 7.5 19.9 16.0 16 7.1 19.9 15.6 17 6.9 19.7 15.2 186.8 19.7 14.8 19 6.7 19.6 14.5 20 6.5 19.5 14.1 21 6.2 19.4 13.9 22 6.119.3 13.5 23 6.0 19.3 13.1 24 5.7 19.1 13.0 25 5.6 18.9 12.6 26 5.5 18.812.2 27 5.4 18.6 11.9 28 5.3 18.5 11.7 29 5.2 18.4 11.6 30 5.0 18.2 11.3

TABLE 8 Average soil moisture retention in soil with our withoutbentonite slurry. Non Wetted Wetted Wetted Soil Control Bentonite SoilSoil AVERAGES −Day 1 9.7 22.7 22.3 AVERAGES Day 30 5.0 18.2 11.3 Changein Soil 4.7 4.5 11.0 Moisture Content % Moisture 52% 80% 51% Retention

1-30. (canceled)
 31. A method of enhancing growth of a plant relative toa control plant, comprising: a) applying a flowable supersaturatedbentonite slurry comprising from about 1% to about 50% w/w of bentoniteand at least about 50% w/w of water into a hole formed in a plant growthmedium to form a supersaturated bentonite slurry plug, wherein thesupersaturated bentonite slurry contains more than the amount of waterrequired for complete saturation of the bentonite as determined by theSwell Index, and the bentonite is completely saturated with the water;b) introducing a plant into the hole formed in the plant growth mediumcontaining the supersaturated bentonite slurry plug such that roots ofthe plant are in contact with the supersaturated bentonite slurry plug;and (c) covering the roots of the plant and the supersaturated bentoniteslurry plug with additional plant growth medium such that thesupersaturated bentonite slurry plug is fully embedded within the plantgrowth medium, and (d) allowing the plant to grow, wherein thesupersaturated bentonite slurry plug retains a higher moisture contentthan wetted soil alone such that growth of the plant is measurablyenhanced relative to a control plant planted in growth medium alone thatis not treated with the supersaturated bentonite slurry plug.
 32. Themethod of claim 31, wherein the growth of the plant is determined by ameasurement selected from the group consisting of plant biomass, totalyield, seed yield, root growth, plant size, total plant dry weight,above-ground dry weight, above-ground fresh weight, leaf area, stemvolume, plant height, rosette diameter, leaf length, root length, rootmass, tiller number, and leaf number.
 33. The method of claim 31,wherein the growth of the plant grown in contact with the bentoniteslurry plug is enhanced under drought conditions.
 34. The method ofclaim 31, wherein the supersaturated bentonite slurry plug furthercomprises at least one compound selected from the group consisting of afertilizer, a plant growth regulator, a fungicide, an insecticide, anamino acid, a peptide, a protein, and a nucleic acid.
 35. The method ofclaim 31, wherein the plant growth regulator is selected from the groupconsisting of auxins, giberellins, cytokinins, ethylene-relatedcompounds, abscisic acid, brassinosteroids, jasmonates, polyamines,karrikins, and any combination thereof.
 36. The method of claim 31,wherein the bentonite of the supersaturated bentonite slurry plug isselected from the group consisting of sodium bentonite and calciumbentonite.
 37. The method of claim 31, wherein the supersaturatedbentonite slurry comprises at least about 50% w/w of water and fromabout 10% to about 50% w/w of bentonite.
 38. The method of claim 34,wherein the fertilizer comprises a micronutrient.
 39. The method ofclaim 31, wherein the plant is selected from the group consisting of aseedling, a transplant, a sapling, and nursery stock of a tree or shrub.40. A method of enhancing growth of a plant relative to a control plant,comprising: a) introducing a plant into a hole formed in a plant growthmedium; b) applying a flowable supersaturated bentonite slurrycomprising from about 1% to about 50% w/w of bentonite and at leastabout 50% w/w of water into the hole formed in the plant growth mediumto form a supersaturated bentonite slurry plug, such that roots of theplant are in contact with the supersaturated bentonite slurry plug,wherein the supersaturated bentonite slurry contains more than theamount of water required for complete saturation of the bentonite asdetermined by the Swell Index, and the bentonite is completely saturatedwith the water; (c) covering the roots of the plant and thesupersaturated bentonite slurry plug with additional plant growth mediumsuch that the supersaturated bentonite slurry plug is fully embeddedwithin the plant growth medium; and (d) allowing the plant to grow,wherein the supersaturated bentonite slurry plug retains a highermoisture content than wetted soil alone such that growth of the plant ismeasurably enhanced relative to a control plant planted in growth mediumalone that is not treated with the supersaturated bentonite slurry plug.41. The method of claim 40, wherein the growth of the plant isdetermined by a measurement selected from the group consisting of plantbiomass, total yield, seed yield, root growth, plant size, total plantdry weight, above-ground dry weight, above-ground fresh weight, leafarea, stem volume, plant height, rosette diameter, leaf length, rootlength, root mass, tiller number, and leaf number.
 42. The method ofclaim 40, wherein the growth of the plant grown in contact with thebentonite slurry plug is enhanced under drought conditions.
 43. Themethod of claim 40, wherein the supersaturated bentonite slurry plugfurther comprises at least one compound selected from the groupconsisting of a fertilizer, a plant growth regulator, a fungicide, aninsecticide, an amino acid, a peptide, a protein, and a nucleic acid.44. The method of claim 43, wherein the plant growth regulator isselected from the group consisting of auxins, giberellins, cytokinins,ethylene-related compounds, abscisic acid, brassinosteroids, jasmonates,polyamines, karrikins, and any combination thereof.
 45. The method ofclaim 40, wherein the bentonite of the supersaturated bentonite slurryplug is selected from the group consisting of sodium bentonite andcalcium bentonite.
 46. The method of claim 40, wherein thesupersaturated bentonite slurry comprises at least about 50% w/w ofwater and from about 10% to about 50% w/w of bentonite.
 47. The methodof claim 43, wherein the fertilizer comprises a micronutrient.
 48. Themethod of claim 40, wherein the plant growth medium is soil.
 49. Themethod of claim 40, wherein the plant is selected from the groupconsisting of a seedling, a transplant, a sapling, and nursery stock ofa tree or shrub.
 50. A method of enhancing growth of a plant relative toa control plant, comprising: a) contacting roots of a plant with aflowable supersaturated bentonite slurry comprising from about 1% toabout 50% w/w of bentonite and at least about 50% w/w of water, whereinthe supersaturated bentonite slurry contains more than the amount ofwater required for complete saturation of the bentonite as determined bythe Swell Index, and the bentonite is completely saturated with thewater; b) introducing the plant into a hole formed in a plant growthmedium; c) covering the roots of the plant and the supersaturatedbentonite slurry with additional plant growth medium such that thesupersaturated bentonite slurry is fully embedded within the plantgrowth medium; and d) allowing the plant to grow, wherein thesupersaturated bentonite slurry retains a higher moisture content thanwetted soil alone such that growth of the plant is measurably enhancedrelative to a control plant planted in growth medium alone that is nottreated with the supersaturated bentonite slurry.